Passive Contact Research Articles

Influence of sex and estrous cycle on the effects of acute tryptophan depletion induced by a gelatin-based mixture in adult Wistar rats

Women are more vulnerable to develop depression and anxiety disorders than men. This may be related to higher serotonergic vulnerability in women. Serotonergic vulnerability entails that differences between people in the regulation of serotonin (5-HT) determine the vulnerability of an individual to develop depression or other 5-HT-related disorders. The aim of the present experiment was to evaluate whether male and female Wistar rats differ in serotonergic vulnerability. Here, a stronger behavioral response to acute tryptophan (TRP) depletion was assumed to reflect serotonergic vulnerability. Twenty-four male and 48 female rats were repeatedly subjected to treatment with a gelatin-based protein–carbohydrate mixture, either with or without l-tryptophan. Female estrous cycle phase was determined by means of vaginal smears and the females were divided into two groups based on their estrous cycle phase: pro-estrus/estrus and met-estrus/di-estrus. Blood samples showed stronger TRP depletion in males than females. There was no effect of estrous cycle on plasma TRP concentrations. In contrast, treatment effects on some brain TRP concentrations were influenced by estrous cycle phase, females in pro-estrus/estrus showed the strongest response to TRP depletion. In the open field test and home cage emergence test, females in pro-estrus/estrus also showed the strongest behavioral response to acute TRP depletion. In general, females showed more activity than males in anxiety-related situations and this effect appeared to be enhanced by TRP depletion. In the social interaction test, passive body contact in males and females in pro-estrus/estrus was decreased after TRP depletion whereas it was increased in females in the met-estrus/di-estrus phase. Acute TRP depletion affected object recognition, but did not affect behavior in the forced swimming test and a reaction time task. It is concluded that sex and estrous cycle phase can influence the behavioral response to TRP depletion, and that females in pro-estrus/estrus show the strongest behavioral response to acute TRP depletion.

Active Opening Force and Passive Contact Force Electrostatic Switches for Soft Metal Contact Materials

This paper reports on a mechanically bi-stable, electrostatically actuated switch mechanism with a large active opening force and a small passive closing force, designed to fit the contact and opening force requirements of soft contact materials such as gold. So far, most microelectromechanical systems (MEMS) switch designs have been optimized for a large contact force without paying too much attention to the opening force. In the "conventional," most commonly used electrostatic microswitch concept, the force of the actuator is used to close the switch contacts, and the switch is opened by the passive restoring force of the deflected cantilever or membrane. This concept results in a large contact force, but the opening force is typically too small to overcome the contact adhesion force of soft metals, which makes this concept less suitable for contact materials such as gold with its low contact resistance at low contact forces. The switch concept presented in this paper is based on two cantilevers laterally moving by curved electrode actuators. The tips of the cantilevers are endowed with hooks which can be mechanically interlocked. In the latched state, the spring forces of the deflected cantilevers also act as the passive contact force between the switch contacts. The opening force is actively created by the curved-electrode actuators, which are utilized close to their best electromechanical operating point resulting in a maximum contact separation force. The theoretical discussion of the new concept as compared to conventional switch designs is supported by simulation results, measurements on fabricated devices, and by an analysis of exemplary switches published in the literature

DEVELOPMENT OF DISPLAY BEHAVIOR IN YOUNG CAPTIVE BEARDED SEALS

AbstractIn this study of the ontogeny of vocal behavior in captive bearded seals, Erignathus barbatus, (three males and three females), only males exhibited vocal displays. The onset of display behavior coincided with sexual maturity. Males exhibited three types of dive displays associated with the performance of vocalizations. Vocalizing individuals were frequently attended by another male that maintained passive muzzle contact with the vocalizing male. These interactions were non‐aggressive and might play a role in the establishment of a social hierarchy or they might allow the attendee to obtain “near‐field” vocal information from the displaying male. Captive males’ vocalizations resembled those of males in the wild. However, display dives were shorter, and fewer vocalization types were documented among the captive males compared to bearded seals in the wild. The capacity of the captive males for producing well‐formed, long calls with large frequency changes was also significantly less than for wild males. These capacities will likely develop further as the males grow older. Individual capacity for vocal production appears to develop gradually, showing plasticity in form development over time.

Digging Behavior of <I>Solenopsis invicta</I> Workers When Exposed to Contact Insecticides

ABSTRACT Contact between ants and insecticides is a prerequisite for contact insecticides to be effective in the control of red imported fire ants, Solenopsis invicta Buren. Typically, passive contact occurs in the insecticide application process, but ants also may actively contact insecticides by digging in treated soil or walking on a treated soil surface. Laboratory experiments were conducted to determine whether fire ant workers would dig sand treated with contact insecticides in two different scenarios: (1) no-choice bioassays where insecticide-treated sand was the only available digging substrate, and (2) two-choice bioassays where nontoxicant sand was also available for digging. Eight insecticides that are currently registered in the United States for imported fire ant control were tested. They include acephate, bifenthrin, carbaryl, cyfluthrin, deltamethrin, gamma-cyhalothrin, permethrin, and pyrethrin. Workers dug the treated sand for every insecticide tested, even at concentrations up to 10 times of the lowest lethal concentration (LLC) which caused 100% mortality in a toxicity bioassay. However, generally, insecticides significantly reduced the digging effort, even at a concentration that did not cause any significant mortality in the toxicity bioassay.

Inhibitory Effects of Korean Red Ginseng and Its Genuine Constituents Ginsenosides Rg3, Rf, and Rh2 in Mouse Passive Cutaneous Anaphylaxis Reaction and Contact Dermatitis Models

The inhibitory effects of the Korean red ginseng (steamed root of Panax ginseng C.A. MEYER, family Araliaceae) saponin fraction (KRGS) and its constituents ginsenosides Rg3, Rf, and Rh2 in mouse passive cutaneous anaphylaxis (PCA) and contact dermatitis models were measured. Orally administered KRGS and its genuine ginsenosides potently inhibited the PCA reaction induced by IgE. However, when these ginsenosides were intraperitoneally administered, ginsenoside Rh2 showed the most potent inhibition. The ginsenoside Rh2 also the most potently inhibited the beta-hexosaminidase release from RBL-2H3 cells induced by IgE with antigen. KRGS administered topically at a dose of 0.1% suppressed ear swelling in an oxazolone-induced mouse contact dermatitis model by 38.8%. Its constituents ginsenosides Rg3, Rf, and Rh2 at a concentration of 0.05% also potently suppressed mouse ear swelling by 47.5%, 34.8%, and 49.9% at 16 d, respectively. These ginsenosides also significantly reduced mRNA expression levels of cyclooxygenase (COX)-2, interleukin (IL)-1beta, tumor necrosis factor-alpha and interferon-gamma induced by oxazolone applied to mouse ears. However, the ginsenosides, except for ginsenoside Rh2, almost did not notably reduce IL-4 levels. The ginsenoside Rh2 also potently inhibited COX-2 and inducible NO synthetase protein expression in liphopolysaccharide-stimulated RAW264.7 cells. Based on these findings, KRGS and its ginsenosides are suggested to improve atopic and contact dermatitis by regulating expression of cytokines.

Solving a fixture configuration design problem using genetic algorithm with learning automata approach

Proper fixture design is crucial to workpiece quality assurance in manufacturing. Incorrect fixture design may lead to workpiece deformation during machining. The fixture configuration design is one of the important aspects of fixture design. This paper deals with fixture layout optimization problem. The objective is to minimize the norm of all the passive contact forces satisfying Coulomb friction constraint, work-piece static equilibrium constraint and contact constraint, for the entire cutting operation. To solve this problem, the paper proposes Genetic Algorithm with Learning Automata (GALA) algorithm, which is a population based interconnected learning automata algorithm incorporating genetic operators. The algorithm enjoys the good characteristics of both GA and LA. It is validated with an example of face milling operation. The optimal layout is found to be in tune with empirical facts. Also, for the further investigation of the algorithm, it has been tested on a different problem sets and a comparative study is carried out.

On the prediction of passive contact forces of workpiece-fixture systems

The prediction of passive forces in a frictional workpiece-fixture system is an important problem, since the contact forces have a strong influence on clamp design and on workpiece accuracy during machining. This paper presents a general method for the computation of passive contact forces. Firstly, an indeterminate system of static equilibrium is defined, in which the passive, frictional contact forces cannot be determined arbitrarily as in an actively controlled robotic multifinger grasp. Then, a locally elastic contact model is used to describe the non-linear coupling between the contact forces and elastic deformations at the contact point. This model captures the essence of the passive contact. Further, a set of ‘compatibility’ equations is given so that the relationship can be developed between the elastic deformations at all contacts and the displacement of the workpiece. Finally, combining the force equilibrium, the locally elastic contact model and the ‘compatibility’ conditions, the passive force computation problem is transformed into a determinate system of non-linear equations governing all of the elastic deformations at all of the passive contacts. By solving the resulting non-linear equations, all passive contact forces can be accurately predicted in the frictional workpiece-fixture system. This method is illustrated with example cases. The method presented here may also have an application to other passive, indeterminate problems such as power grasps in robotics.

Metal sintering mechanisms and regeneration of palladium/alumina hydrogenation catalysts

We have investigated the role of different Pd sintering mechanisms on the regeneration process for alumina supported Pd hydrogenation catalysts. The Pd sintering mechanisms are strongly influenced by the catalyst morphology. In the case of fresh catalyst, Pd particles sit directly on the alumina surface and sintering occurs via a traditional ripening and coalescence mechanisms and was significant only at 600 °C or above. For the used catalyst, Pd particles are supported mostly on green oil residue and this dramatically changed the sintering mechanism during the regeneration process. Catalytic gasification of green oil residue around the Pd particles in an oxidizing environment permits movement and coalescence to take place at relatively low temperatures. During the stripping, Pd particles are passively brought into contact as hydrocarbon is gasified and the exothermic nature of the process raises the temperature to about 500 °C. At this temperature, chance contact between metal particles results in rapid coalescence and gives rise to particle sintering even at temperatures well below the Tamman temperature. This passive contact process is the dominant mechanism for Pd coarsening during catalyst regeneration.

Role of oxytocin and vasopressin in the transitions of weaning in the rat

Sucklings (18-day-old) and weanlings (35-day-old) were injected icv with oxytocin or its antagonist (both 0.5 microg/1 microl), or vasopressin (1.0 ng/1 microl) or its antagonist (100 ng/1 microl), prior to 4-min observation in a behavioral maze with a sibling in one box and their anesthetized dam in the other. Oxytocin abolished nipple attachment in sucklings, decreased time spent with the dam, and increased self-grooming. The oxytocin antagonist had little influence on behavior. Vasopressin increased self-grooming while its antagonist reduced passive contact with the dam, increased active contact with her, and increased exploration and activity. We conclude that these neuropeptides have diverse roles during weaning, maintaining sucklings' behavior or promoting weaning, and subserving the transition from attachment to the dam to independence from her. We propose that these neurochemicals, and others, mediate the neural, affiliative, and affective changes of weaning, and that the term "weaning" should be understood to encompass these behavioral transitions.

Mother-Infant Interactions in Slow Lorises (Nycticebus bengalensis) and Pygmy Lorises (Nycticebus pygmaeus)

The study had three purposes: (1) to obtain information about mother-infant interactions in a rarely studied nocturnal prosimian, the pygmy loris (Nycticebus pygmaeus); (2) to compare pygmy lorises with a closely related and better-studied nocturnal prosimian, the Bengal slow loris (Nycticebus bengalensis); and (3) to determine how the presence of a second offspring affected mother-infant interactions in pygmy lorises. Three Bengal slow loris mothers and 3 pygmy loris mothers served as subjects, along with their 10 offspring (4 Bengal slow loris singletons, 2 pygmy loris singletons and 2 sets of pygmy loris twins). Observations were carried out in a zoo research facility for the first 24 weeks of the infants’ lives. Although the two species differ in size and reproductive patterns, mother-infant interactions were similar. The primary modes of infant and adult contact were ventral and passive contact, respectively. Mothers parked their infants from the first week, and infants followed from the second week. Mothers displayed little protection or rejection, and there was little aggression. Infants solicited play and social grooming from their mothers. Pygmy loris mothers engaged in social grooming and play with their infants more frequently and for longer periods if the infant was a singleton rather than a twin.

Contact Force Prediction and Force Closure Analysis of a Fixtured Rigid Workpiece With Friction

Analysis and characterization of workpiece-fixture contact forces are important in fixture design since they define the fixture stability during clamping and strongly influence workpiece accuracy during manufacturing. This paper presents a method for predicting and analyzing the normal and frictional contact forces between workpiece-fixture contacts. The fixture and workpiece are considered to be rigid bodies, and the model solution is solved as a constrained quadratic optimization by applying the minimum norm principle. The model reveals some intricate properties of the passive contact forces, including the potential of a locator release and the history dependency during a sequence of clamping and/or external force loading. Further, a notion of passive force closure is considered to characterize the passive nature of the fixture forces. Geometric conditions for two types of passive force closure (concordant and discordant closures) are provided, showing a complication of released locator under clamping with a limited role in force closure. Model predictions are shown to be in good agreement with known results of an elastic-contact model prediction and experimental measurements. The passive force closure conditions are illustrated with examples. This presented method is conceptually simple and computationally efficient. It is particularly useful in the early stages of fixture design and process planning.

A comparison of rapid village survey and leprosy elimination campaign, detection methods in two districts of East Java, Indonesia, 1997/1998 and 1999/2000

A Rapid Village Survey (RVS) was planned to estimate the extent of the leprosy problem in two well documented endemic districts of East Java, Indonesia. Furthermore, the aim was to investigate the efficacy of the routine programme in detecting new and early cases, as well as the feasibility of RVS in detecting disabled people affected by leprosy in the community. A random sample survey (RVS: a simple method compared to a Population Sample) was used to determine the extent of the leprosy problem. In addition, a Leprosy Elimination Campaign (LEC), was used particularly to detect new and backlog cases in the community. Both RVS and LEC involve a health education campaign followed by the examination of persons voluntarily reporting. Routine programme case finding, involving passive case finding and contact examinations, was also carried out. The RVS prevalence rate of 12 per 10,000 was more than twice the known prevalence rate of 5 per 10,000. The LEC prevalence rate was less than the rate found by RVS, but was within the RVS confidence interval. During the RVS, many children with leprosy were detected, and 10% of all RVS new cases already had disability grade II. The population disability grade II rate due to leprosy was 9 per 10,000. Despite the fact that an active leprosy control programme had been carried out in the surveyed endemic area over a period of many years, the actual prevalence rate found was more than twice the known prevalence. Many children were found during the RVS, thus indicating continuing widespread transmission. In general, it seems that there is still a serious delay in detecting new cases under the routine programme. Consequently, there are substantial numbers of persons affected by leprosy in those districts in need of rehabilitation.

Migration through host cells activates Plasmodium sporozoites for infection

Plasmodium sporozoites, the infective stage of the malaria parasite transmitted by mosquitoes, migrate through several hepatocytes before infecting a final one. Migration through hepatocytes occurs by breaching their plasma membranes, and final infection takes place with the formation of a vacuole around the sporozoite. Once in the liver, sporozoites have already reached their target cells, making migration through hepatocytes prior to infection seem unnecessary. Here we show that this migration is required for infection of hepatocytes. Migration through host cells, but not passive contact with hepatocytes, induces the exocytosis of sporozoite apical organelles, a prerequisite for infection with formation of a vacuole. Sporozoite activation induced by migration through host cells is an essential step of Plasmodium life cycle.

Regulation of the hypothalamic-pituitary-adrenal axis in the neonatal rat: the role of maternal behavior.

There is a growing literature that indicates that exposure to elevated levels of glucocorticoids can result in long term consequences for the developing brain. In the developing rodent there is a period from about day 4-14 when the adrenal response to stress is either minimal or non-existent thus resulting in stable low levels of circulating glucocorticoids. This has been designated as the stress hypo-responsive period (SHRP). Numerous experiments have demonstrated that maternal factors are critical for the regulation of the pup's hypothalamic-pituitarty adrenal (HPA) axis and the maintenance of the SHRP. Following 24 h of maternal deprivation the neonatal rat shows elevated basal levels of corticosterone and exhibits a robust corticosterone and ACTH response to mild stress. Further c-fos mRNA in the paraventricular nucleus is enhanced following stress in deprived pups. At least three aspects of maternal behavior play a role in the regulation of the HPA axis during development. Tactile stimulation appears capable of inhibiting most of the brain-related changes that occur following maternal deprivation. Feeding is essential for maintaining the adrenal unresponsive and reduces the sensitivity of the adrenal to ACTH. Passive contact suppresses the response to stress. In the adult corticotropin-releasing hormone (CRH) is the major neuropeptide that controls pituitary ACTH secretion. In the maternally deprived pup CRH gene transcription is down regulated and arginine vasopressin (AVP) appears to assume the major regulatory hormone that modulates ACTH. These data all indicate that maternal factors are responsible for actively inhibiting the endocrine responses to stress postnatally. Further, maternal deprivation also results in increased cell death in several brain regions. Thus during development most of the peripheral and central stress responsive systems are capable of being activated. However, under conditions of normal dam-pup interactions these responses are mostly suppressed by the dam's behavioral interaction with the pups thus preventing the potential toxic effects of increased secretion of glucocorticoids during critical periods of brain development.

Primary social relationships influence the development of the hypothalamic–pituitary–adrenal axis in the rat

In the developing rodent, there is a period from about days 4 to 14 when the adrenal response to stress is either minimal or non-existent. This has been designated as the stress hyporesponsive period (SHRP). Numerous experiments have demonstrated that maternal factors are critical for the regulation of the pup's hypothalamic–pituitary–adrenal (HPA) axis and the maintenance of the SHRP. Following 24 h of maternal deprivation, the neonatal rat shows elevated basal levels of corticosterone (CORT) and exhibits a robust CORT and ACTH response to mild stress. Further, c- fos mRNA in the paraventricular nucleus (PVN) is enhanced following stress in deprived pups. At least three aspects of maternal behavior play a role in the regulation of the HPA axis during development. Tactile stimulation appears capable of inhibiting most of the brain-related changes that occur following maternal deprivation. Feeding is essential for maintaining the adrenal-unresponsive and reduces the sensitivity of the adrenal to ACTH. Passive contact suppresses the response to stress. In the adult, corticotropin-releasing hormone (CRH) is the major neuropeptide that controls pituitary ACTH secretion. In the maternally deprived pup, CRH gene transcription is downregulated and arginine vasopressin (AVP) appears to assume the major regulatory hormone that modulates ACTH. These data all indicate that maternal factors are responsible for actively inhibiting the endocrine responses to stress postnatally. Thus, during development, most of the peripheral and central stress-responsive systems are capable of being activated. However, under conditions of normal dam–pup interactions, these responses are mostly suppressed by the dam's behavioral interaction with the pups.

A new experimental approach to assess settlement conditions in tube-building polychaetes; biological implications

The present paper proposes an original experimental procedure for studying the processes occurring during larval settlement. This procedure is based on fractionalising the settlement period by isolating part of the available substratum and on using a sediment-marker that dramatically increases the contrast between the tubes and the background. Our approach overcomes two methodological difficulties in the study of tube-building organisms: the temporal isolation of observations that occults the continuity of settlement processes and the lack of precise estimates of the initial number of benthic individuals. Our results demonstrate that, in the tube-building polychaete Eupolymnia nebulosa, settlement in still water consists of an initial passive contact of larvae with the bottom followed by an active reorganisation of the larval distribution. This second phase is connected with the ability of larvae to return to the water column after an initial contact with an unsuitable substratum. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS settlement / recruitment / laboratory experiments / time fractionalising / larva-substratum relationship

A unified approach to non-holonomic dynamics

Dynamical problems subject to non-linear non-holonomic constraints are analyzed using the differential variational principles of Jourdain (JVP) and Gauss (GVP). In contrast with linear non-holonomic constraints which arise from passive contact or rolling constraints, non-linear non-holonomic constraints (NNHC) arise in problems where the constraints are actively imposed, such as control or servo-constraints, consideration of some first integrals as kinetic side conditions, or mathematical constraints without regard to their physical realizability. To date, such problems have been treated by various ad hoc and unrelated methods in a fragmented manner, without a unifying idea running through the various methods of approach. In the present paper, it is shown that by applying the JVP to velocity constraints, and the GVP to acceleration constraints, dynamical problems subject to NNHC can be handled in a uniform way. Both the method of constraint embedding (elimination of variations) and constraint adjoining (use of Lagrange multipliers) are used in analyzing the behavior of the dynamical system subject to NNHC.

Environmental Enrichment for New World Primates: Introducing Food-Irrelevant Objects and Direct and Secondary Effects

This study examined methods of environmental enrichment for zoo animals for 4 New World primate species: pygmy and Geoffrey's marmosets (Cebuella pygmaea and Callithrix geoffroyi), red-bellied tamarins (Saguinus labiatus), and golden- headed lion tamarins (Leontopithecus chrysomelus). Subjects were housed in groups at the Philadelphia Zoo. Baseline behavioral time budget data were collected, and stimulus objects were then introduced in succession to each enclosure. Each object included multiple manipulable subcomponents. Time budget data were collected while objects were in the enclosures, and subjects' contacts with objects were videotaped. Overall time budgets were significantly altered in only the red-bellied tamarins, the least active of the species, solely due to a shift from social grooming to passive social contact; when categories were collapsed into broader categories, this effect disappeared. Object contact occurred within the 1st hr for all species and ranged over nearly 2 orders of magnitude, from approximately 10 sec per subject (red-bellied tamarins) to approximately 700 sec per subject (Geoffrey's marmosets). Habituation was not evident within any 1st hr of observation but was shown when 1st hr observations were compared with those from subsequent days. This article discusses implications for environmental enrichment in zoos.

Age effects on the social interaction test in early adulthood male rats

The effects of age on active and passive social interaction were studied in Wistar rats using the social interaction test (S.I.T.). Individual behaviors such as ambulation, rearing, and defecation were also studied. Despite the widespread use of the S.I.T. in anxiety research, the effects of age on the S.I.T have not been studied thoroughly. Male Wistar rats of 75, 135, and 180 days old were used. Our results showed age effects on active social contact, passive social contact, ambulation, rearing, and defecation. At 135 days old, animals presented the lowest scores on active social behavior and the highest scores on defecation. Moreover, exploratory behavior measured by ambulation and rearing decreased with age. These results suggest that age could be a relevant variable in the social interaction test. Depression and Anxiety 12:226–231, 2000. © 2000 Wiley-Liss, Inc.

Age effects on the social interaction test in early adulthood male rats

The effects of age on active and passive social interaction were studied in Wistar rats using the social interaction test (S.I.T.). Individual behaviors such as ambulation, rearing, and defecation were also studied. Despite the widespread use of the S.I.T. in anxiety research, the effects of age on the S.I.T. have not been studied thoroughly. Male Wistar rats of 75, 135, and 180 days old were used. Our results showed age effects on active social contact, passive social contact, ambulation, rearing, and defecation. At 135 days old, animals presented the lowest scores on active social behavior and the highest scores on defecation. Moreover, exploratory behavior measured by ambulation and rearing decreased with age. These results suggest that age could be a relevant variable in the social interaction test.